The MoD is seeking to create a single corporate brand identity to promote the divisions, such as those representing military police, scientists and engineers.
The contract will start from next May and is part of a search for agency support for all marketing, advertising and comms efforts, estimated to be worth around £3m.
It has not yet been decided whether a group of specialists, including a PR agency, or one agency that can provide a full service will be appointed.
Divisions involved in the contract include the Defence, Engineering and Science Group (DESG), Defence Procurement Agency, Defence Estates, Defence Science and Technology Laboratory, and the Armed Forces Land Command.
The pitch process is being co-ordinated by Tom Williams who takes up the role of DESG marketing manager at the MOD's Bath headquarters next week.
Kay Winstone, current marketing manager, who moves next week to a role advising Geoff Hoon on the euro, said: 'We need to see who's out there and what they can provide. One option will be to have one PR agency that different groups can call on when they need to.'
She added that the creation of an MOD corporate brand next year was to make the work of the department's civilian divisions easier for the public to understand, and to help recruitment.
The briefing document for agencies seeking to tender adds that specialist press knowledge is essential due to the specialised nature of many of the MoD's civilian posts.
PR for recruiting to the divisions is currently handled in-house. The deadline for tendering is 20 December.